000
AGPN40 KWNM 091557
MIMPAC
Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
757 AM PST FRI DEC 9 2016
.FORECAST DISCUSSION...Major features/winds/seas/significant
.weather for the North Pacific N of 30N and E of 150W.
At 12Z complex low presure system just north and northwest of the
waters has an associated occlusion inland over northern California
and northward with trailing cold front extending southwest from
Point Arena into a stationary front west of central PZ6 waters.
Lightning data show some activity with the low south of the Queen
Charlottes and also west of 138W near the stationary front. Clouds
become more convective in cold advection north of the front
especially in PZ5 waters. Previous high resolution ASCAT-B image
showed the 06Z GFS first sigma level winds are
representative...especially in the area north of the front. Winds
are mostly light south of the front where a weak area of high
pressure is parked over the central and southern PZ6 areas.
For the morning update with previous grids based on earlier GFS
repopulated wind grids with more current and representative 06Z
GFS first sigma level winds through Saturday when the latest
models are in agreement taking the main low out near 50N139W east
into Vancouver Island with slow weakenings and with only minor
edits with moderate to high confidence will maintain marginal
gales entering portions of the northern and central PZ5 waters
associated with that main low. Gales should end in the far
northeast Saturday evening. After that low weakens near western
Washington with residual trough extending west and norethwest
through Monday. Continued using 06Z GFS 30m winds but blended with
the somewhat lower 10m winds.
In the extended portion Tuesday and Tuesday night continued use of
the 00Z ECMWF which is supported by the UKMET and 00Z global GEM
with GFS appearing too progressive taking a low east along the
stationary front into the PZ6 waters by Tuesday.
Seas...Repopulated seas with the slightly more representative 00Z
ECMWF WAM with the 06Z ENP WW3 substantially too low near the to
northwest of Vancouver Island initially. After 06Z Sunday used a
50/50 blend with the 06Z ENP WW3 and then after Monday to be
consistent with wind grids transitioned to 00Z ECMMWF WAM.
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PREVIOUS DISCUSSION...
The latest IR satellite picture still has fairly cloudy skies
across the central regions and clearing continues over the north
waters while almost clear skies are still over the southern
waters. The lightning density map has continued to show no
indication of TSTMS over the forecast region and the SREF model
still has PROB 0 for severe TSTMS across the region but will
increase to PROB 10 over the far north waters tonight. The latest
observations including scatterometer pass about 0548Z indicate
higher winds over the north waters with maximum winds still in the
mid gale force range. At 06z the NCEP map now has low pressure 988
mb near 50N 140W with its occludded front stretching SE across the
north waters into inland then continues SE as a warm front while
its cold front stretches SW into the central region which is
inline with the depiction of the satellite imagery. The winds in
the south sector of the low pressure are within storm force
threshold. The southern waters are dominated by high pressure 1024
mb centered just east of the central waters. Farther west near 43N
167E is low pressre 984 mb with hurricane force winds while high
pressure 1032 mb is near the central pacific. Meanwhile, the
pressure gradient over the forecast waters is still fairly slack
over most of the region except the far north waters.
In the upper levels the models GFS/CMC/ECMWFHR/UKMETHR still
suggest a band of energy has stretched southeast from an
upperlevel low near 50N 150W into the north waters. A weak
upperlevel ridge with little to no energy covers the central and
southern waters. In the short term there will be lingering energy
over the north waters that will keep a tight presssure gradient
causing persistantly tight pressure gradient. The senario will
persist into the extended period.
The 00Z models GFS/CMC/NOGAPS/UKMETHR/ECMWFHR have initialized
the 06Z surface observations fairly well and they continue to be
in agreement in the short term on pushing low pressure from the NW
toward the north waters. There are still small differences mainly
on the pressure field associated with the peak value within 2 MB
for the complex low pressure just northwest of WA waters. These
small differences do not alter the general synoptic pattern in the
short term. In the extended period the models have some
differences on the progression of the low pressure over the
central pac that will be approaching the waters from the
southwest. GFS has low pressure in the waters sooner than the rst
of the models and so will stay with GFS only in the short term
then will switch to the ECMWFHR just before end of period.
.SEAS...The seas are largest over the NW portion of the WA waters
with peak at 13 ft. Seas are smallest over the far south waters
where they range between 2 and 4 ft. Both NWW3 and ECMWFWAVE
models fit very well with the observed seas pattern and they have
been quite consistent in the previous runs. The wave models are
also in good agreement over the short term on building the seas
over the north waters. A blend of both wave models will still be
used for this forecast and the plan is not to deviate much from
the prvious model choice. So will go with a blend of both wave
models. In the short term will remain large over the north waters
with peaks at 17 ft but will start to subside sat.
.EXTRATROPICAL STORM SURGE GUIDANCE...
.WARNINGS...Preliminary.
.PZ5 Washington/Oregon Waters...
.PZZ800...Inner Waters from Cape Flattery to Cape Shoalwater...
Gale tonight into Saturday night.
.PZZ900...Outer Waters from Cape Flattery to Cape Shoalwater...
Gale tonight into Saturday night.
.PZZ805...Inner Waters from Cape Shoalwater to Cape Lookout...
Gale Saturday into Saturday night.
.PZZ905...Outer Waters from Cape Shoalwater to Cape Lookout...
Gale tonight into Saturday night.
.PZ6 California Waters...
None.
$$
.Forecaster Bancroft/Musonda. Ocean Prediction Center.